Recovery of recombinant virus. (A) Digestion of full-length BAC cDNA clone prSCV with the restriction enzyme Bgl I. The BAC construct had seven Bgl I restriction sites at positions 4454, 8783, 12146, 19000, 24124, 31719, and 36168, resulting in 7 digestion fragments as annotated in the gel picture: 7595 bp (infectious clone Fragment F as identified in Figure 3A with appending BAC fragment [digestion fragment 1]); 6854 bp (Fragment D, ); 5124 bp (Fragement E, ); 4972 bp (Fragment A with appending BAC fragment, ); 4449 bp (BAC fragment, ); 3362 bp (Fragment C, ); 4330 bp (Fragment B, ) (B) Analysis of supernatants taken from BHK cells 24 h after transfection with in-vitro transcripts from the BAC cDNA clone. Supernatant was diluted as indicated and plated on Vero cells. The top panel shows the results of indirect immunofluorescence analysis using a human polyclonal antiserum. The bottom panel shows the results of plaque assays on the same Vero cells. (C) Electron micrograph of Vero cells infected as described above. (D) Detail from (C).